Working on the trainwreck

[lastwinj]

built it up about a month ago, but had some noise. so, i am going to rewire it, and make a few changes. here are a few pics. i call her elena.

[IMG:160:60]http://i53.photobucket.com/albums/g66/lastwinj/th_elena003.jpg[/img]
[IMG:158:60]http://i53.photobucket.com/albums/g66/lastwinj/th_elena004.jpg[/img]
[IMG:160:78]http://i53.photobucket.com/albums/g66/lastwinj/th_elena005.jpg[/img]
[IMG:160:74]http://i53.photobucket.com/albums/g66/lastwinj/th_elena006.jpg[/img]



thanx for looking!!

germ

[keithrick]

Germ, what kind of noise? Look at the Francesca pics in the Files section. Layout is key to the build.

[lastwinj]

Germ, what kind of noise? Look at the Francesca pics in the Files section. Layout is key to the build.

made a stupid mistake, and wired the heaters as 6.3, and the tranny i had custom made was 12.6v.... DOH!! i do forget things at times. so had to rewire with it looking like that. not an easy wiring job, and it probably introduced some noise. so, all has been riped out and going to start from scratch.

thanx!!

germ

[Funkalicousgroove]

I don't mean to sound overly critical, because we've all gotta start somewhere, but you may want to read up on Lead dress. Building Valve Amps by Morgan Jones is an excellent reference. You will find that keeping certain things in certain places away from other things makes a big difference not only in the noise floor of the amp, but in the overall harmonic content and sound as well. Improper lead dress can result in parasitic oscillation, noise, cross-talk etc.

You want to keep plate wires away from grid wires, and if they must cross it should be at 90degree angles. Signal carrying wires should be as short as possible, and not necessarily near the chassis.

Also, read the "Trainwreck Pages" in the files section, Ken talks about improving the tone of your Marshall by moving wires around, but those techniques work well on other amps as well.


How does it sound???

[Dai H.]

lol... i think he knows what he is doing...

[Funkalicousgroove]

Perhaps he does, I just cringe everytime I see grid and plate wires run paralell to eachother. I certainly meant no offense

[Dai H.]

I suppose the wire lengths look a bit long and unkempt which might give someone the impression of noobishness, but I'm just speaking from the perspective of seeing his other stuff like high gain preamps and such. I guess it's a bit messy (the striped wire probably makes it look worse, lol...) but generally the layout looks logical.

BTW, I'm curious to your rationale behind the grid and plate wires. What is the reason you consider that bad?

[Funkalicousgroove]

Read this: http://www.geofex.com/Article_Folders/l ... e_amps.htm

[Dai H.]

well I was hoping for your opinion not RG's but thx

[Funkalicousgroove]

To tell you the truth, I read alot of books to learn about tubes since it's 1930's technology. I also learned about lead dress the hard way on my first couple of builds. So, anything I could possibly say about the subject has already been said, argued over, etc. I found that in my first couple of builds where I had lots of long wires going everywhere that the amps would oscillate, get "Ghost notes" be NOISY, and sound generally displeasing. I had a tech friend look at one and he said that my problem was most likeley lead dress, so I read what alot of different folks had to say on the subject, and I talked to alot of builders, and found that most of them had the same basic things to say:

Plate wires can be longer, but grid wires should be as short as possible.
Since the plate lead is not only carring the DC voltage to the plate,but also carrying the amplified version of the signal that is going through the grid lead it only seemed logical that the same phase cancellation that occurs when you twist your heater wires and keeps them quiet could occur between the plate and grid leads if they were ran close together, or that the stronger AC signal flowing through the Plate lead could "Impose" itself on the earler stage and modulate it or cause wolf tones.

I'm not an engineer, just a fellow that loves to build amps, and from what folks who buy them tell me, they're pretty fantastic sounding. I'm not out to prove anything, prove anyone wrong, or re-invent the wheel-just to help if I can.

I had a Two-Rock once that was an absolute Spaghetti factory inside, when I'd turn the knobs up with nothing plugged in it would hiss and hum and make all kinds of spaceship noises, at lower volumes it was fine, but those strange oscillations bothered me so I sold it. Years Later when I finished my first Dumble Clone (Which was basically the same circuit) I had an opportunity to compare it with that same Two-Rock, and the D-Clone sounded MUCH better, it had a much more rounded musical sound to it, the cleans were Hi-Fi, almost harpsichord like. That amp is Dead quiet with all knobs cranked. The biggest difference in the two was the Lead Dress, and I just followed what I had been told.

[Chad]

Thank's for the link Funk. After reading it I've got a better understanding about lead dress.I've learned before lead dress is crucial to having a less noise in a amp, but that seemed to make it a little more clear why. Again Thank's. Chad

[lastwinj]

thanx dai. i appreciate the kind words.

in the pics it looks as if things are close, but i keep grids and plates at least 1/2inch away from each other. that far away is usually sufficient, even if in parallel. agreed that it looks a bit messy. i will be fixing that soon. the chassis is an 18w from komboking, so a true "ken Fischer" layout can;t be done. (

noise was just a nasty buzz. i'm 95% sure it was from my heater wires not being clean (read about the messup in wiring...) also, the volume control just jumped to DAMN loud from zero. i am using clarostat Z taper pots, which are true audio pots, IIRC. the 100pf bright cap didnt do a thing, either.

doesn't really matter now. the amp has been torn apart, and rewiring will commence. woohoo!!!


germ

[Dai H.]

Funkalicousgroove...

okay, it sounds like you're saying this, as a rule:

Perhaps he does, I just cringe everytime I see grid and plate wires run paralell to eachother.

(please correct me if I'm misunderstanding, but you are saying) IOW they shouldn't because they can couple, and that can cause problems and therefore it should not be done.

But, how do you explain cases where you see an actual capacitor used (or a capacitance)? If coupling is absolutely wrong then why would this be the case? Or, with some old marshalls, you might see the grid wire wrapped around the plate wire.


hey germ...

[Normster]

Well first off, Hi Germ and welcome to our nightmare! I'm gonna go out on a limb and assume that you're the same Germ that sent a preamp to Jim Heidinger? (He raved about it for weeks.)

As for lead dress and layout in general, I've tried to copy from pictures and then reason why the designer did it that way. So far I've built 4 Dumble clones copying routing, grounding, and layout from available images. All of them have been very quiet and performed pretty well. After seeing pics of Franscesca, I've decided to build an Express just because the layout and routing are so elegant. Since the whole design philosophy is different between the amps, I'm really curious to hear the noise level in the Express. (Who knows, it may motivate me to rethink my Dumbles. )

[lastwinj]

Well first off, Hi Germ and welcome to our nightmare! I'm gonna go out on a limb and assume that you're the same Germ that sent a preamp to Jim Heidinger? (He raved about it for weeks.)

As for lead dress and layout in general, I've tried to copy from pictures and then reason why the designer did it that way. So far I've built 4 Dumble clones copying routing, grounding, and layout from available images. All of them have been very quiet and performed pretty well. After seeing pics of Franscesca, I've decided to build an Express just because the layout and routing are so elegant. Since the whole design philosophy is different between the amps, I'm really curious to hear the noise level in the Express. (Who knows, it may motivate me to rethink my Dumbles. )

yep, thats me.

i have always followed the philosophy: Keep everything away from everything, and run the shortest possible route to a connection, if allowed. from this standpoint, ugly can be a good thing.

germ